Videographers routinely lose their margin in the editing phase, not the shoot. Scope creep during revisions is what quietly turns a profitable flat-rate project into an unprofitable one, so a sustainable pricing model has to define the exact number of revision rounds and the exact length of final deliverables before the project starts, not after.
Day rates for shooting also need to cover equipment amortization. Cameras, lenses, and lighting degrade and eventually become obsolete, so a percentage of every invoice should go toward a dedicated equipment replacement fund before you calculate personal profit on top. Put the revision limit directly in your contract or estimate, and use the change order generator to bill anything beyond the agreed rounds as a separate, paid addition.